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[Sticky] Creating a Bad Pixel Map  

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(@uwe1475)
Brown Dwarf Customer
Joined: 3 years ago
Posts: 9
April 21, 2020 21:43  

WOW what a great function !!!! I have always wondered what that is good .. I always tried it on the stacked picture and in full view .. but never in 100% view and on individual lights.
Great thank you!


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
April 21, 2020 22:04  

It is a really nice feature yes, you can play around and check the effect before stacking. Same with flats applied or not.


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(@uwe1475)
Brown Dwarf Customer
Joined: 3 years ago
Posts: 9
April 21, 2020 22:16  

Yes, so you can see if the flats are "working"
Just experimenting with it, which raised the question of what happens when I select "L-C-Registered" ?? Registering means aligning several lights with each other exactly, or am I confusing something? But I can only display 1 picture at a time. And I can see no changes between "L-Calibratet" and "L-C-Registered".
And what does "Normalized" or how do I normalize a light? I have already changed everything under 5) Normalize but I see no difference between Registered and Normalized.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
April 21, 2020 22:22  

L-C-registered is useful after registration is done. You can then go through the frames 1 by 1 to check if that worked. Or after registering a mosaic, checking what it did, change that if required and check again.


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(@uwe1475)
Brown Dwarf Customer
Joined: 3 years ago
Posts: 9
April 21, 2020 22:40  

@vincent-mod

Madness! Thanks for your help. You helped me a lot.


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(@fendium)
White Dwarf Customer
Joined: 2 years ago
Posts: 13
August 20, 2020 00:30  

Is it useful to create multiple BPM for different iso settings of a DSLR?

I have two session of imaging with a canon EOS-6d, one at 3200iso, one at 6400iso

For each one i have acquired flat, bias, dark, so i create two set of masters. I use multi-session processing and APP let me to assign each master to a specific session, but not for BPM. APP seems to accept and use only one BPM: when i open a BPM file APP assign this file to all lights, and does not ask for which session.

 

Is that correct?

APP BPM

 

 

 

 


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
August 22, 2020 14:32  

Good question, I don't think so no. A BPM will never be harmful for your data, so take the longest dark with the most noise to make it and it should work.


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(@dave23913)
Brown Dwarf Customer
Joined: 10 months ago
Posts: 9
September 7, 2020 16:41  

I have a question regarding the creation of the BPM. I've read that it requires the use of Dark frames and Flat frames, and that once created, it can be used many times (~ 1 year) before needing to create a new one. My question...Dark frames are typically taken after the Lights using the same exposure parameters under the same temperature conditions. But if the BPM file can be used over and over again, this would imply that exposure length and temperature condition is not important when creating the Dark frames needed for creation of the BPM. Is this correct? If so, it would also seem appropriate to use a very long exposure in order to heat up the sensor, making bad pixels more apparent - does that make sense?

Thanks


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
September 9, 2020 12:24  

The creation of a BPM isn't depended really on the conditions indeed. Ideally you take a few really long darks to get all the possible noise that can occur on your sensor. As a BPM is never destructive this will get you a better BPM.


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(@karl-h)
Brown Dwarf Customer
Joined: 10 months ago
Posts: 6
November 16, 2020 21:52  

Hello ,

is it correct that in version 1.082 the BPM is always created and automatically applied?

CS Karl

This post was modified 7 months ago by Karl H kower

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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
November 16, 2020 22:06  

Yes, a BPM is now created automatically if the correct masters are available. You can copy/move that BPM to a folder where you also store your darks if you want, darks and a BPM can be used for multiple sessions. A BPM even for at least 6 months.


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(@karl-h)
Brown Dwarf Customer
Joined: 10 months ago
Posts: 6
November 16, 2020 22:22  

Thanks !

unfortunately I cannot load and see a finished stack result fits another session to test this BPM?

still V8.02..... do I have to delete all flats and darks first to load a finished stack?

This post was modified 7 months ago by Karl H kower

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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
November 16, 2020 22:36  

You can load the BPM and just another single light, zoom in to the pixels on the BPM, then double-click the single light to load it in and switch between the normal view and "L-Calibrated" from the drop-down menu on top of APP. L-calibrated will show you what your calibration masters will do with that single light. It's a fast way to check if your calibration is working nicely.


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(@karl-h)
Brown Dwarf Customer
Joined: 10 months ago
Posts: 6
November 16, 2020 23:18  

sorry Vincent , I made a mistake, it works fine

But I have again the question: does it really make a difference to use BPM and darks, bias and flats?


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
November 17, 2020 01:07  

Yes, it does. It will depend a little on the sensor, but when you zoom in just a little and then apply all those calibration files you'll see that difference yourself with the method I described above. It will remove a lot of the fixed pattern noise in your data. Flats will probably have the biggest effect of them all (when created properly which can be a bit of a challenge sometimes). You can correct for vignetting and dust with those. When properly calibrated you'll be able to stretch a bit more, get a nice signal out of the data etc.


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(@karl-h)
Brown Dwarf Customer
Joined: 10 months ago
Posts: 6
November 17, 2020 12:40  

Thanks Vincent !

I will try it !


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(@karl-h)
Brown Dwarf Customer
Joined: 10 months ago
Posts: 6
November 19, 2020 13:45  

Hello again,

Now I have one more question:

if the BPM is always created automatically anyway Is it still worthwhile to create a special one with, for example, a longer Darks exposure time? Does this then have to be exchanged for the automatically generated one?

CS karl

 


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3439
November 19, 2020 15:07  

Best is to use a BPM with something like a long exposed dark and even a good flat (if you have any cold pixels) and loading that in before starting to process. No BPM will be created then but the one you provided is used.


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(@gordoabc)
Hydrogen Atom Customer
Joined: 6 months ago
Posts: 1
January 2, 2021 02:25  

I am just starting up the learning curve for Astrophotography and APP and started by making a bad pixel map for my Canon EOS R.  I was a bit surprised to see 2.9% cold pixels given this should qualify as a recent sensor.  I have 1.8% hot pixels which seems fine.  I made a white T-shirt flat at ISO 100, 1/250 s (50x), bias at ISO100 1/8000s (50x), and black at ISO100, 300s (50x).  I loaded into APP and created masters using the default settings (hot pixel kappa 3 and cold pixels 10%).  I think what I am getting may be some kind of CR3 artifact since the image size for APP is 6888x4546 which is quite a bit larger than nominal 6741 x 4494.  The bad pizel map seems to have cold pixels along the top and left hand side which roughly account for the 2.9% as can bee seen in the screen shot.  It appears the BMP is masking out some part of the sensor that isn't functional?  Since I am new to this I want to be sure since the BMP will be used for every image going forward and I'd hate to have messed it up somehow.

Screen Shot 2021 01 01 at 5.53.27 PM

FYI screen shot was from a second attempt using cold fraction 50% just to see if it made a difference (it didn't).

 

This post was modified 6 months ago 2 times by Thomas Mason

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(@wvreeven)
Galaxy Admin
Joined: 3 years ago
Posts: 852
January 2, 2021 11:48  

Canon cameras have a region to the top and left of the sensor that don’t collect light and serve as a way for the camera to determine the black point of the sensor. Normally these regions are not read out and in your case account for the larger image size.

APP processes the images as they are and doesn’t introduce any additional pixels. What software did you use to take the images? I’d suggest you talk to the manufacturer of that software to discuss this issue.


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